Ethane Vs. Ethene

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Ethane

• Part of the alkane homologous group (General formula )
• Saturated molecule
  • Since it is saturated it is harder to react and overall, much more chemically stable (compared to Ethene)
• Comes as a flammable, odorless gas

Ball-and-Stick model of Ethane

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Ethene (Common name: Ethylene)

• Part of the alkene homologous group (General formula)
• Unsaturated molecule
  • Since it is unsaturated it will react easier over the double bond and thus is less chemically stable (compared to Ethane)
  • Much more reactive
  • Due to double bond, will undergo addition reactions

Ball-and-Stick model of Ethene

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Properties

Similarities:

Both Ethane and Ethene (And extended, the alkane and alkene homologous series) similiar physical properties
i.e.

• Boiling Point
• Melting Point
• Densities
• Solubility

Differences:

Ethene and Ethane have vastly different chemical reactivity

i.e.

• Ethane
  • Undergoes substitution reactions (where a H will be replaced with another element, i.e. Cl or Br)
• Ethene
  • Undergoes addition reactions (where the double bond breaks and other elements "add" onto it)

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Testing for Alkenes and Alkanes

Because of these differences, we can test for Ethane and Ethene (Alkanes/Alkenes) through the use of bromine solutions;

• Ethane
  • The solution will decolourise in the presence of UV light (slowly), thus in the absence of UV light, it will not decolourise
• Ethene
  • The solution will rapidly react decolourise as the bromine will react with the ethene (through an addition reaction)

By using this, we can test to see if there is any Ethane left in a solution